Set during the reign of King Sukjong in the Joseon dynasty, the story focuses on Dong Yi, a water maid who gains the trust of Queen Inhyeon and later the favour of the king when he is moved by her prayers for the health of the Queen during the court disputes caused by Jang Hee Bin. Dong Yi becomes a concubine with the rank of sook-bin and bears a son who will later become the 21st king of Joseon, Yeongjo.
Han Hyo Joo as Dong Yi, later Choi Sook-Bin
Kim Yoo Jung as Dong Yi (child)
Ji Jin Hee as King Sukjong
Bae Soo Bin as Cha Chun Soo
Lee So Yeon as Jang Hee Bin
Park Ha Sun as Queen Inhyeon
Jung Jin Young as Seo Yong Gi
Kim Hye Sun as Court Lady Jung
Choi Ran as (Hee Bin's mother)
Lee Jung Gil as Oh Tae Suk
Lee Kye In as Oh Tae Poong
Kim Yoo Suk as Jang Hee Jae
Park Jung Soo as Queen Myeongseong (Sukjong's mother)
Jung Sung Woon as Dong Joo
Choi Soo Han as Ge Dwo Ra
Choi Chul Ho as Oh Yoon
Jung Yoo Mi as Jung Im
Kim Hye Jin as Seol Hee
Jung Sun Il (정선일) as Park Doo Kyung
Chun Ho Jin as Choi Hyo Won